A trunk network illustratively comprises a plurality of node interconnected by transmission links. Two technological advances have had a substantial impact on the trunk network. These ar the extensive deployment of high-bandwidth fiber optic transmission links and the deployment of reconfigurable digital cross-connect nodes. (See, e.g., Rodney J. Boehm, et al, "Standardized Fiber Optic Transmission Systems - A Synchronous Optical Network View", IEEE Journal on Selected Areas in Comm., Vol. SAC-4, No. 9, December 1986; Satoshi Hasegawa et al, "Dynamic Reconfiguration of Digital Cross-Connect Systems With Network Control and Management", GLOBECOM '87) Typically, each reconfigurable digital cross-connect node includes a digital cross-connect switch and configuration table which determines how the links incident to the node are interconnected by the cross-connect switch.
The new technologies have increased the need for survivability strategies in the event of the failure of one or more network components. In particular, the aggregation of traffic which has been accelerated by the deployment of high-bandwidth fiber-optic transmission links has increased the amount of damage which can be caused by a single failure. The accidental severing of a single fiber-optic cable can disrupt tens of thousands of connections. Fortunately, the deployment of reconfigurable digital cross-connect nodes together with the abundant capacity of fiber links greatly increases the ability of a trunk network to recover from failure events. After a fiber-optic cable has been cut or a digital cross-connect node fails, it is possible to use the surviving nodes to reconfigure the network to restore much of the lost call-carrying capacity.
In view of the foregoing, it is an object of the present invention to provide a distributed protocol for maintaining the call-carrying capacity of a telecommunications trunk network after the failure of certain network components. In particular, it is an object of the present invention to provide a distributed protocol which is executed at each node of a trunk network comprising high-bandwidth optical fiber links and reconfigurable digital cross-connect nodes for maintaining the call-carrying capacity of the network in the event of a single or multiple node or link failure.